<!Doctype html>
<html>
<style>
    #container {
        width: 400px;
        height: 400px;
        position: relative;
        background: yellow;
    }
    #animate {
        width: 50px;
        height: 50px;
        position: absolute;
        background: red;
    }
</style>
<body>

<h1>JavaScript</h1>

<div id="container">
    <div id="animate"> aa </div>
</div>

</body>
</html>
